The Effects of Microhabitat on Population Structure and Morphology
One of my first findings was a difference in size associated with microhabitat. Nonpit urchins, on average, are larger than pit urchins. Explanations for this observation include differential growth rates between microhabitats, a tendency for urchins to move out of pits as they grow, or higher mortality rates - perhaps because of predation - inside pits.
I also found that pit and nonpit urchins differ in their morphology, with pit urchins having significantly shorter spines, larger jaws, and greater test height:diameter ratios than nonpit urchins. It is important to note that in many species of urchins, larger relative jaw size has been attributed to food limitation, so it is possible that sea urchins receive less food when they live inside rather than outside pits.
The pit urchin, on the left, has relatively shorter spines and a larger height:diameter ratio compared to the nonpit urchin on the right. These urchins came from the same tidepool.
